Answer:
Many of the internal processes in our body occur without our conscious awareness. Our stomach digests food, our lungs take in oxygen and exhale carbon dioxide, and our kidneys filter our blood each and every day. Our internal organs and systems work automatically, and it is likely that whole days go by when we don't pause to think of our insides at all.
However, one major bodily system may catch our attention more often because we can feel it working in certain parts of our body. Our pulse, rhythmic pulsing of blood through our arteries, is a constant reminder that, at any given moment, blood is coursing through each and every part of us. Our bloodstream is part of our circulatory system, which consists of the heart and blood vessels that carry blood throughout our body. In this lesson, we will learn more about the important vessels that return blood back to the heart after traveling to our body parts. These vessels are called veins.
Explanation:
